The invention relates to a testing apparatus for in situ calibration of pressure gauges, comprising a reference chamber for connection of the pressure gauge to be tested, a calibrated pressure sensor connected to the reference chamber, and a regulating means connected to a gas supply unit and arranged to regulate the pressure in the reference chamber.
Current fields of use of such an apparatus are e.g. control of altimeters in aircrafts and control of pressure gauges which are used to measure gas deliveries for production platforms for hydrocarbons. The pressure gauges may be constructed to measure absolute pressure, manometric pressure or differential pressure.
According to what one knows, there has not been developed mobile equipment having sufficient precision and stability to operate in the field for control/calibration of high-precision pressure gauges. Thus, common practice is to disassemble the pressure gauges at given time intervals and send these to a laboratory for a fresh control/calibration (with e.g. a "dead weight tester"). This circumstantial procedure is a natural consequence of the fact that, outside specially equipped laboratories, it is difficult to procure relevant test conditions.
One has tried various solutions with respect to procuring acceptable conditions for pressure calibration at the place of use. One has, for example, connected the pressure gauge in question and a precision pressure sensor to a common chamber of which the pressure may be regulated by means of a movable piston. It has, however, appeared to be difficult to obtain the pressure stability over time which is necessary, because even very small gas leakages or temperature changes have influence on the calibration (i.e. the pressure). Traditional pressure regulators neither has shown to be suitable in this context since the degree of regulation is too small.